In this movie the past is unchangeable , no matter how many times he went back Alexander could not save his fiancé . The death of his fiancé is what caused him to create the time machine; without that event he would have never gone back in the first place .A linear time paradox ( like the grandfather paradox) (H.G. Wells)
First of all If we could build a time machine is the past unchangeable ? Or does a multiverse exist ? Different time lines in a string of pearls; with multiple paths, choices and outcomes. Time is to be said by many philosophers to be an entirely illusory construct created by man to begin with anyways ,but the march of entropy still continues !